A typical process for making cast resin epoxy insulators is the automatic pressure gelation process (APG process). The APG process requires that before injecting the reactive mixture into a hot mold the curable system comprising the epoxy resin composition (composition A) as well as the composition comprising the hardener for the epoxy resin (composition B) have to be prepared to be ready for injection.
In ease of pre-filled systems, i.e. a system having compositions which comprise a filler, the composition must be stirred up in the delivery container due to the sedimentation of the filler in the composition. Typically, in order to obtain a homogeneous formulation the filler containing composition has to be heated up and stirred. After homogenization of each composition of the curable system the compositions are combined and transferred into a mixer and mixed at elevated temperature and a reduced pressure in order to degas the formulation. The degassed mixture is subsequently injected into the hot mold.
In case of non-pre-filled systems the epoxy resin composition and the hardener composition are typically mixed individually with the filler and optionally further additives at elevated temperature and reduced pressure to prepare the pre-mixture for the resin and the hardener. In a further step the two compositions are combined to form the final reactive mixture, typically by mixing at elevated temperature and reduced pressure. Subsequently, the degassed mixture is injected into the mold.
However, the APG process known in the prior art requires several steps, i.e. at least a stirring step in order to avoid the sedimentation of the filler and additionally a degassing step.
In the field of silicone process technology curable systems are where two compositions are pumped at ambient temperature out of the respective delivery containers without degassing or prestirring through a static mixer into a mold. The mixing and dosing equipment is sufficient to fulfil the requirements to process the two compositions in order to prepare a reactive mixture which can be injected into a mold. Depending on the size of the article to be prepared the respective volume is injected through a static mixer into the mold.
The basic design of all silicone injection systems is composed of a base frame to hold the different compositions. The compositions can be stored in commercially available drums. A hydraulic control ensures a synchronous operation of the dosing pumps.
The existing curing systems cannot be applied to the “silicone processes”.